Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path: <python.list@tim.thechases.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.013
X-Spam-Evidence: '*H*': 0.97; '*S*': 0.00; 'mrab': 0.05; 'cherrypy': 0.09; 'subject:skip:c 10': 0.09; 'subtle': 0.09; 'def': 0.12; '-tkc': 0.16; 'from:addr:python.list': 0.16; 'from:addr:tim.thechases.com': 0.16; 'from:name:tim chase': 0.16; 'lambda': 0.16; 'fix': 0.17; 'wrote:': 0.18; 'decorators': 0.24; 'cc:2**0': 0.24; 'cc:no real name:2**0': 0.24; 'pass': 0.26; 'header:In-Reply-To:1': 0.27; 'that.': 0.31; 'apparently': 0.31; 'not.': 0.33; "i'd": 0.34; 'case,': 0.35; 'but': 0.35; 'charset :us-ascii': 0.36; 'thanks': 0.36; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'either': 0.39; 'making': 0.63; 'happen': 0.63; 'helping': 0.70; 'difference.': 0.84; 'received:50.22': 0.84
Date: Tue, 29 Oct 2013 12:54:05 -0500
From: Tim Chase <python.list@tim.thechases.com>
To: python-list@python.org
Subject: Re: stacked decorators and consolidating
In-Reply-To: <526FF395.9040306@mrabarnett.plus.com>
References: <20131029115427.537e1bcd@bigbox.christie.dr> <526FF395.9040306@mrabarnett.plus.com>
X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.10; x86_64-pc-linux-gnu)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - boston.accountservergroup.com
X-AntiAbuse: Original Domain - python.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - tim.thechases.com
X-Get-Message-Sender-Via: boston.accountservergroup.com: authenticated_id: tim@thechases.com
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.1769.1383069148.18130.python-list@python.org>
Lines: 27
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1383069148 news.xs4all.nl 15975 [2001:888:2000:d::a6]:49636
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:57946

On 2013-10-29 17:42, MRAB wrote:
> If you apply the stacked decorators you get:
> 
>      myfun = dec1(args1)(dec2(args2)(dec3(args3)(myfun)))
> 
> If you apply dec_all you get:
> 
>      myfun = dec1(args1)(dec2(args2)(dec3(args3)))(myfun)
> 
> See the difference? You need the lambda to fix that.

In this case, they happen to be CherryPy decorators:

  @cherrypy.expose()
  @cherrypy.tools.json_in()
  @cherrypy.tools.json_out()
  def myfunc(...): pass

I'd have figured they would be associative, making the result end up
the same either way, but apparently not.  Thanks for helping shed
some light on the subtle difference.

-tkc